Generally, lighter-than-air vehicles, hereinafter airships, are powered by externally mounted propulsion systems. These propulsion systems typically take the form of a plurality of independent gas or electric powered propeller modules. These propeller modules are sometimes movable in multiple axes in order to direct the flow of air and thereby steer the airship.
Prior art airships further include a gondola mounted at the bottom of the airship, which provides a passenger compartment, storage areas and the like. Airships of this nature are typically employed for a variety of purposes including advertising and transportation. Because the gondola is essentially a rigid body and includes a rigid outer frame, they provided the most suitable location to mount the propeller modules.
Recently, the need has become apparent for airships that travel to greater heights than traditional airships. Such high altitude airships serve a multitude of functions including, but not limited to, communications, weather tracking and intelligence gathering. Particular concerns arose in development of such vehicles, including the need for extended flight durations over an area of interest. Extended flight times are accomplished by controlling high altitude airships autonomously or from an external location, thereby eliminating the need for human presence on the airship. Because human operators are no longer required on the airship, the traditional gondola became unnecessary. Further, traditional gondolas are relatively heavy, and conflict with the need to make the airship extremely light. For these reasons, the traditional gondola was replaced by a much smaller bay or external mounting surface, which holds the computer airship controls, communication equipment and mission specific equipment such as cameras, sensors and the like.
Propulsion in high altitude airships is accomplished using electrically powered motors coupled to external propellers. With the removal of the gondola from the airship, the traditional mounting point for propulsion modules was likewise removed, leaving no rigid structure on which to attach the propulsion system. Hence, the need became apparent to mount the propeller modules directly to the fabric skin of the airship. High altitude airships employ a flexible outer fabric skin or membrane for hull construction. A membrane has very little rigidity normal to its surface. This compliance makes it difficult to attach propeller modules with the stiffness that they need to react against the various loads such as thrust, weight, and torque. Furthermore, the fabric skin is a difficult surface to mount articles particularly because internal pressures within the airship change with ascent and descent. As the internal pressures change, the exterior fabric skin rigidity changes.
Therefore, there exists a need in the art to effectively attach external articles, and particularly external propulsion systems that impart significant loads such as thrust, weight, and torque, to the fabric skin exterior of high altitude airships.